GSGS (Series) ; 3868. 3rd ed. "Revised 1938. (Grid change only, 1945.)" "Air Survey by the R.A.F. and ground control by 2nd Colonial Survey Section, R.E., 1924-25. Field Revision by P.W.D. Hong Kong 1932, and by R.E. Survey Section, 1935-37. Plotted by the Geographical Section, General Staff, 1930. Drawn and heliographed at the Ordnance Survey 1930, 1939. Photolithographed by O.S. 1945." World polyconic projection.
